The aim of this project is to obtain structural information on polynucleotides and other polymers and to provide insights into the factors which control structure, principally through X-ray fiber diffraction and model building studies. Current areas include 1) analysis of the unique structure adopted by the RNA-DNA hybrid, poly (rA).poly(dT) in highly hydrated samples using X-ray fiber diffraction techniques; 2) X-ray survey of other RNA-DNA hybrids in highly hydrated circumstanaces; 3) determination of the helical parameters by X-ray methods for a polymer, poly d(G-5 methyl C), which adopts the Z form; 4) an X-ray examination of the intermediate filaments from Chinese hamster ovary cells; 5) collaboration in a joint NMR and X-ray diffraction study of natural and synthetic polynucleotides.